The use of carbon fiber/carbon matrix composite disk brakes, commonly referred to as carbon/carbon composite disk brakes in the braking industry is extensively known. Thermal characteristics and the braking efficiency of such braking systems account for their wide spread acceptance in such industries as the aircraft industry. However, those skilled in the art realize that carbon/carbon composite brakes are expensive, a large portion of the costs incident thereto being the labor intensity required in the manufacture of the carbon/carbon composite disks themselves. Carbon/carbon composite brake disks are formed of fibers which are provided in the form of a tow (bundle of continuous filament) or in a roving (a bundle of many short filaments). These fibers may be derived from either pitch or PAN. Those skilled in the art readily understand that pitch fiber is one in which a thermoplastic derivative of coal tar or petroleum pitch is spun into fiber which is subsequently carbonized by an appropriate technique or method for driving the volatiles therefrom. Poly acryol nitrile fibers, commonly referred to as PAN fibers, are oxidized, carbonized, and appropriately heat treated. Both pitch and PAN fibers are well known and extensively used in the manufacture of carbon/carbon composite disks for braking systems.
The state of the art for the manufacture of carbon/carbon composite disks for the braking industry is fairly shown in U.S. Pat. Nos. 5,686,117 and 6,083,436. There, effective methods and apparatus for forming such carbon/carbon composite disks are shown. However, the techniques of certain of the prior art are time-consuming and the resultant structures often exhibit less than optimum performance.
An important step in the manufacture of carbon/carbon brake disks is densification of the disk by introducing carbon material into the gaps, openings and crevices that characterize the interwoven array of carbon fibers of the tow or roving forming the disk. Such is typically achieved by chemical vapor infiltration (CVI), a time-consuming process. In accordance with the invention, CVI densification time may be reduced by modifying the shape and size of such gaps, openings and crevices and thereby increasing the surface areas therein to which carbon material may bind during CVI or other densification process.
It has been found that disk rubbing surfaces other than of a homogeneous carbon/carbon material may give rise to improved performance as to braking efficiency, thermal dissipation, and wear. In that regard, additives to the tow or roving forming the disk may be employed to achieve such beneficial results. Such additives should, most desirably, be tolerant of high temperatures, and should create desirable performance characteristics.
It has further been found that homogeneous carbon/carbon disks are given to vibrations. According to the invention herein, such vibrations may be dampened or substantially eliminated by interposing an appropriate filler as a center layer.
There is a need in the art for carbon/carbon brake disks manufactured with the use of fillers that hasten the manufacturing process, enhance performance, and substantially dampen vibrations.